1. Field of the Invention
This invention relates to radiant tubes for use in heating various materials such as steel pieces, other kinds of solid matters, or fluids in a heating furnace.
2. Description of the Prior Art
In the conventional radiant tube, when high-temperature gases produced by a burner are supplied into the tubular radiator section from one end thereof, the radiator section is increased in its temperature to radiate heat. The gases thus used for heating the radiator are then discharged from the other end thereof.
When thus flowing out of the radiator, the gases still have a higher temperature; accordingly, in the past, the inventors herein made an attempt to recover heat from the exhaust gases by locating a heat exchanger within the radiator in a position nearer to its exhaust end. Such a heat exchanger, however, is of a lower temperature so that it may reduce the temperature of its surroundings. Such a lowering of the temperature of the radiator prevents the satisfactory heat radiation for heating the materials.